Method of reproducing multimedia data and multimedia data server system

ABSTRACT

In a method for reproducing multimedia data recorded over plural optical disks, using an optical disk library unit having at least two, first and second, optical disk drives, multimedia data recorded in one of the optical disks is read and reproduced in the first optical disk drive and, during the reading and reproduction, the next optical disk is mounted in the second optical disk drive. Reading and reproduction of multimedia data recorded in the next optical disk mounted in the second optical disk drive are started immediately after the reading of the multimedia data recorded in the optical disk in the first optical disk drive is completed. Therefore, it is possible to continuously reproduce the multimedia data without interruption due to exchange of the optical disks.

This is a Division of application Ser. No. 08/748,657 filed Nov. 14,1996 and now is U.S. Pat. No. 5,805,538.

FIELD OF THE INVENTION

The present invention relates to a method of reproducing multimedia datarecorded over plural optical disks, using an optical disk library unitcontaining an optical disk drive or plural optical disk drives, and amethod of reproducing multimedia data in response to plural requests forreproduction, using an optical disk library unit including at least oneoptical disk drive. The invention also relates to a multimedia serversystem equipped with an optical disk library unit that deals with pluraloptical disks using an optical disk drive or plural optical disk drives,in which a server distributes multimedia data recorded in the opticaldisks to plural clients.

BACKGROUND OF THE INVENTION

In recent years, multimedia server systems have attracted a lot ofattention. In a typical multimedia server system, a plurality ofmultimedia data including, for example, image data, voice data, andcharacter data, are recorded in a storage device and, on a server-clientsystem network, the server reads out the multimedia data from thestorage device in response to the client's request and transmits thedata to the client wherein the data is reproduced. In such a multimediaserver system, when moving image data is transmitted, a sufficientlyhigh transmission speed is required for continuous reproduction of thedata. Hence, the storage device is desired to perform high-speed readingand writing of data. However, a high-speed storage device, such as ahard disk, is expensive. Since the multimedia server system needs a massstorage device, such as an RAID using a plurality of hard disks, theprice of the system increases significantly. In order to spread themultimedia server system by reducing the price, in recent years, amultimedia server system employing, as a mass storage device, a libraryunit that deals with plural optical disks, which are cheeper than harddisks, has been developed.

A description is now given of a multimedia server system employing anoptical disk library unit, and a method of reproducing multimedia datain the system.

FIG. 27 is a block diagram illustrating a prior art multimedia serversystem employing an optical disk library unit. In FIG. 27, referencenumeral 500 designates an optical disk library unit containing aplurality of optical disks wherein a plurality of multimedia data arerecorded. These multimedia data are data including image data andcompressed according to a format based on general MPEG method. Referencenumeral 400 designates a server, numeral 600 designates clients, andnumeral 650 designates a network connecting the server 400 to theclients 600. The server 400 reads multimedia data from the optical disklibrary unit 500 in response to requests from the clients 600 anddistributes the data to the clients 600. The clients 600 request theserver 400 to read multimedia data, receive the multimedia data, andreproduce the multimedia data. Reference numeral 550 designates aconnection between the optical disk library unit 500 and the server 400,on the basis of SCSI (Small Computer System Interface) standard or thelike.

FIG. 28 is a schematic diagram illustrating the structure of the opticaldisk library unit 500. In FIG. 28, reference numeral 501 designates anoptical disk in which multimedia data is recorded, and the recordedmultimedia data is processed for a logical block as a unit. Referencenumeral 502 designates a storage shelf comprising plural slots, eachcontaining an optical disk. Reference numeral 503 designates an opticaldisk drive for reading multimedia data from the optical disk 501 orwriting multimedia data in the optical disk 501. Reference numeral 504designates a conveyer for conveying the optical disk 501 between thestorage shelf 502 and the optical disk drive 503. Reference numeral 505designates a controller for controlling the conveyer 504 and the opticaldisk drive 503 on the instruction of the server 400.

FIG. 29 is a block diagram illustrating the structure of the server 400.In FIG. 29, reference numeral 401 designates a library control means forcontrolling the optical disk library unit 500 connected to the server400. Reference numeral 402 designates a control means for controllingreading and transmission of multimedia data in response to the requestsof the clients. Reference numeral 403 designates a data transmitting andreceiving means for exchanging data with the clients through the network650. Reference numeral 404 designates a recording content storage meansstoring a title specifying multimedia data, an optical disk in which themultimedia data is recorded, and a position on the optical disk wherethe multimedia data is recorded.

FIG. 30 is a block diagram illustrating the structure of the client 600.In FIG. 30, reference numeral 601 designates a reproduction requestaccepting means for accepting a request for reproduction of multimediadata from a user. Reference numeral 602 designates a data reproducingmeans for reproducing multimedia data sent from the server 400 anddisplaying the data on a display unit 603.

Reference numeral 604 designates a data transmitting and receiving meansfor exchanging data or requests with the server 400 through the network650.

FIG. 31(a) shows the data structure of information stored in therecording content storage means 404 within the server 400. As shown inFIG. 31(a), the recording content storage means 404 stores a title ofeach multimedia data recorded in an optical disk, information foridentifying the optical disk in which the multimedia data having thetitle is recorded (hereinafter referred to as an identification numberof the optical disk), a logical block address showing the position onthe optical disk where the multimedia data is recorded, and a slotnumber showing the position of the optical disk in the storage shelf502.

FIG. 31(b) shows examples of the stored data. In this case, multimediadata with a title "multi05" is recorded in an optical disk "disk#3" in aposition from a logical block 0 to a logical block 8911, and thisoptical disk is contained in a slot #11 in the library unit.

FIG. 32 is a flowchart for explaining a method for reproducingmultimedia data using the prior art multimedia server system.

Initially, in step 1, a user requests reproduction of multimedia data tothe reproduction request accepting means 601 in the client 600 bydesignating the title of the multimedia data, for example, "multi05".

In step 2, the request for reproduction of "multi05" is transmitted fromthe reproduction request accepting means 601 to the data transmittingand receiving means 604. Further, the request is transmitted through thenetwork 650 to the server 400. In the server 400, the request from theclient 600 is received by the data transmitting and receiving means 403,and the control means 402 checks the data in the recording contentstorage means 404 to find the optical disk having the multimedia datarequested by the client 600. More specifically, since the recordingcontent storage means 404 stores the data shown in FIG. 31(b), thecontrol means 402 finds the identification data of the optical disk, thestorage position of the optical disk, and the position of the requesteddata on the optical disk, on the basis of the title "multi05" of therequested multimedia data. In this case, the control means 402 findsthat the desired multimedia data "multi05" is recorded in a range fromlogical block address 0 to logical block address 8911 on the opticaldisk "disk#3" contained in the slot #11 in the storage shelf.

In step 3, the control means 402 confirms, through the library controlmeans 401, whether the optical disk "disk#3" is mounted in the opticaldisk drive 503 in the optical disk library unit 500. When the opticaldisk is not mounted in the drive 503, in step 4, the control means 402instructs the library control means 401 to convey the optical disk"disk#3" from the slot #11 of the storage shelf 502 to the optical diskdrive 503. When the optical disk "disk#3" is already mounted in theoptical disk drive 503, the control means 401 proceeds to step 5.

In step 4, the library control means 401 controls the optical disklibrary unit 500 so that the optical disk "disk#3" in the library unit500 is conveyed from the storage shelf 502 to the optical disk drive503. The controller 505 in the optical disk library unit 500 controlsthe conveyer 504 to take the optical disk "disk#3" from the slot #11 ofthe storage shelf 502 and insert the optical disk in the optical diskdrive 503.

After confirming whether the optical disk "disk#3" is mounted in thedrive 503, the control means 402 proceeds to step 5. In step 5, thecontrol means 402 instructs the optical disk library unit 500 to readmultimedia data, through the library control means 401, on the basis ofthe logical block address obtained from the recording content storagemeans 404. In the optical disk library unit 500, the controller 505instructs the optical disk drive 503 to read multimedia data from thedesignated logical block address 0. Then, the server 400 receives themultimedia data read from the optical disk, and the data transmittingand receiving means 403 transmits the multimedia data, through thenetwork 650, to the client 600, followed by step 6.

In step 6, the multimedia data is received by the data transmitting andreceiving means 604 in the client 600 and reproduced by the datareproducing means 602.

Next, in step 7, it is judged whether all the data recorded in thelogical block addresses 0-8911 are reproduced. When the reproduction isnot completed yet, the above-mentioned reading, transmission, andreproduction of the multimedia data are repeated.

In the method for reproducing multimedia data using the prior artnetwork system, when the multimedia data requested by the client isrecorded in a single optical disk, this data can be continuously outputfrom the server and continuously reproduced in the client. However, ifthe requested multimedia data is recorded over plural optical disks,reading and transmission of this data are not performed when the opticaldisks are exchanged. Consequently, reproduction of the data isunfavorably interrupted due to the exchange of the optical disks.

As described above, the optical disk library unit can store a mass ofmultimedia data at a relatively low cost. However, in many cases,multimedia data, such as image and voice, is recorded over pluraloptical disks. Hence, such an interruption in reproduction of multimediadata is an undesirable matter for the multimedia server system.

A description is now given of a case where plural clients request forreproduction of multimedia data from a single optical disk at the sametime. It is assumed that two lines of MPEG1 data respectively recordedon an outer circumference and an inner circumference of an optical diskare reproduced using an optical disk drive having the followingperformances: maximum seek time of about 750 msec; maximum rotationwaiting time of about 30 ms; effective transmission rate in a range from520 KBytes/sec (inner circumference) to 1150 KBytes/sec (outercircumference).

In order to reproduce the two data lines continuously, data of 187KBytes/sec must be read out from both the inner circumference and theouter circumference. The maximum time required for the reading iscalculated as follows:

    ______________________________________    data reading time =    rotation waiting time * 2 + inner circumference data    transmission time + outer circumference data    transmission time + seeking time =    30 * 2 + 187/520*1024 + 187/1150*1024 + 750 (ms) =    1344 (ms) =    1.3 (s)    ______________________________________

Since the data reading time exceeds one second, it is not possible toread out data at a sufficient speed for continuous reproduction. Thatis, in this case, reproduction of multimedia data is interrupted. Asmentioned above, the possibility of reproduction in response to pluralrequests from plural clients to a single recording medium depends on therecording medium and the performance of the device processing therecording medium, i.e., it depends on the speed of reading or writingdata on the recording medium. Therefore, when plural clients request, atthe same time, reproduction of multimedia data recorded in a high-speedstorage device, such as a hard disk (magnetic disk), the storage devicecan deal with the requests. However, when an optical disk drive having arelatively low data reading speed is employed, if the clients' requestsfor reproduction of data concentrate on a single optical disk, thereproduction is unfavorably interrupted as described above.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method forcontinuously reproducing multimedia data recorded over plural opticaldisks.

Another object of the present invention is to provide a method forreproducing multimedia data, that can avoid unwanted interruption inreproduction when plural requests for reproduction of multimedia dataare received, by checking the requests given to multimedia data recordedon the same optical disk and refusing the request that exceeds theperformance of the optical disk drive.

Still another object of the present invention is to provide a multimediaserver system that can continuously distribute multimedia data recordedover plural optical disks, to clients, by a server equipped with anoptical disk library unit.

A further object of the present invention is to provide a multimediaserver system that can avoid unwanted interruption in reproduction whenplural requests for reproduction are received, by checking whether ornot the requests concentrate on the same optical disk to exceed theperformance of the optical disk drive.

Other objects and advantages of the invention will become apparent fromthe detailed description that follows. The detailed description andspecific embodiments described are provided only for illustration sincevarious additions and modifications within the scope of the inventionwill be apparent to those of skill in the art from the detaileddescription.

According to a first aspect of the present invention, in a method forreproducing multimedia data recorded over plural optical disks, using anoptical disk library unit having at least two, first and second, opticaldisk drives; multimedia data recorded in one of the optical disks isread and reproduced in the first optical disk drive and, during thereading and reproduction, a next optical disk is mounted in the secondoptical disk drive; and reading and reproduction of multimedia datarecorded in the next optical disk mounted in the second optical diskdrive are started immediately after the reading of the multimedia datarecorded in the optical disk in the first optical disk drive iscompleted. Therefore, it is possible to continuously reproduce themultimedia data without interruption due to exchange of the opticaldisks.

According to a second aspect of the present invention, in theabove-mentioned method, the order of the plural optical disks toreproduce the multimedia data from the optical disks, and a timerequired for the reproduction of the multimedia data from each opticaldisk are stored; the operating state of each optical disk drive in theoptical disk library unit is stored; the multimedia data recorded in theoptical disk in the first optical disk drive is read and reproduced;during the reading and reproduction, the next optical disk is mounted,according to the stored reproduction order, in the second optical diskdrive that is judged as usable on the basis of the stored operatingstate of the second optical disk drive, when the remaining reproductiontime of the optical disk in the first optical disk drive, which time isobtained by subtracting the time taken by the reproduction from thestored time required for the reproduction, is longer than the timerequired for exchange of optical disks; and reading and reproduction ofthe multimedia data recorded in the next optical disk mounted in thesecond optical disk drive are started immediately after the reading ofthe multimedia data recorded in the optical disk in the first opticaldisk drive is completed.

According to a third aspect of the present invention, in theabove-mentioned method, the order of the plural optical disks toreproduce the multimedia data from the optical disks is stored; for eachoptical disk, an optical disk drive used for reading and reproduction ofthe multimedia data from the optical disk, and a period of time theoptical disk drive is used are decided and stored as reservation data;and the optical disk is mounted in the optical disk drive according tothe stored reproduction order and the reservation data when the presenttime reaches the decided time and, thereafter, the multimedia data isread and reproduced from the optical disk.

According to a fourth aspect of the present invention, in a method forreproducing multimedia data recorded over plural optical disks, using anoptical disk library unit having at least one optical disk drive; duringreading and reproduction of the multimedia data recorded in one of theoptical disks, the multimedia data from the optical disk is prefetchedby an amount larger than an amount equivalent to the time required forexchange of the optical disks, and the prefetched data is temporarilystored; and the multimedia data stored temporarily is read andreproduced when the optical disk is exchanged for the next optical disk.Therefore, it is possible to continuously reproduce the multimedia datawithout interruption due to exchange of the optical disks.

According to a fifth aspect of the present invention, in theabove-described method, the order of the plural optical disks toreproduce the multimedia data from the optical disks, and a timerequired for the reproduction of the multimedia data from each opticaldisk are stored; the multimedia data is read and reproduced from one ofthe optical disks in the optical disk drive and, at the same time, themultimedia data is prefetched from the optical disk by an amount largerthan an amount equivalent to the time required for exchange of theoptical disks, and the prefetched data is stored temporarily; themultimedia data stored temporarily is read and reproduced and, at thesame time, the next optical disk is mounted in the optical disk driveaccording to the stored reproduction order, when the remainingreproduction time of the optical disk, which time is obtained bysubtracting the time taken by the reproduction from the stored timerequired for the reproduction, becomes shorter than the time requiredfor exchange of optical disks; and reading and reproduction of themultimedia data from the next optical disk is started immediately afterthe reading of the multimedia data stored temporarily is completed.

According to a sixth aspect of the present invention, in theabove-described method, the order of the plural optical disks toreproduce the multimedia data from the optical disks, and a timerequired for the reproduction of the multimedia data from each opticaldisk are stored; one of the optical disks is mounted in the optical diskdrive, and a prefetching speed for prefetching the multimedia data fromthe optical disk, which speed enables a prefetching within a time rangeobtained, is calculated by subtracting the time required for exchange ofthe optical disks from the stored time required for reproduction; themultimedia data is prefetched from the optical disk at the calculatedspeed and temporarily stored and, thereafter, the multimedia data storedtemporarily is read and reproduced; the next optical disk is mounted inthe optical disk drive according to the stored reproduction order,during the reading and reproduction of the multimedia data storedtemporarily, when the remaining reproduction time of the optical disk,which time is obtained by subtracting the time taken by the reproductionfrom the stored time required for the reproduction, becomes shorter thanthe time required for exchange of optical disks; and reading andreproduction of the multimedia data from the next optical disk arestarted immediately after the reading of the multimedia data storedtemporarily is completed.

According to a seventh aspect of the present invention, in theabove-described method, the order of the plural optical disks toreproduce the multimedia data from the optical disks is stored; beforethe reading and reproduction of the multimedia data from one of theoptical disks, a prefetching start position of the optical disk iscalculated, which position enables prefetching of the multimedia data byan amount larger than an amount equivalent to the time required forexchange of the optical disks, during the reading and reproduction; themultimedia data is read and reproduced from the optical disk in theoptical disk drive and, when the recording position on the optical diskreaches the prefetching start position, the multimedia data isprefetched from the prefetching start position and then storedtemporarily; reading and reproduction of the multimedia data storedtemporarily are started when the prefetching of the multimedia datarecorded in the optical disk is completed and, during the reading andreproduction, the next optical disk is mounted in the optical disk driveaccording to the stored reproduction order; and reading and reproductionof the multimedia data from the next optical disk are startedimmediately after the reading of the multimedia data stored temporarilyis completed.

According to an eighth aspect of the present invention, in theabove-described method, when the reproduction of multimedia data isperformed according to a request for reproduction designating areproduction start position and the reproduction start position is, as arecording position on the optical disk, after the prefetching startposition, multimedia data recorded between the prefetching startposition and the reproduction start position are prefetched and storedtemporarily, in advance of reading and reproduction according to therequest. Therefore, unwanted interruption in the reproduction due toshortage of the multimedia data temporarily stored is avoided, and arequest for reproduction in a wider range can be accepted.

According to a ninth aspect of the present invention, in theabove-described method, during reading of the multimedia data from theoptical disk in the optical disk drive, the next optical disk is movedto a storage place nearest to the optical disk drive in the optical disklibrary unit. In this method, since the time required for exchange ofthe optical disks is reduced, the amount of the multimedia data storedtemporarily is reduced, resulting in a reduction in power consumption ofa storage unit used for the temporary storage. Therefore, unwantedinterruption in the reproduction due to exchange of the optical disks isavoided with less hardware resources.

According to a tenth aspect of the present invention, in a method forreproducing multimedia data in response to plural requests forreproduction of multimedia data, using an optical disk library unithaving at least one optical disk drive, when a new request forreproduction of multimedia data is given to the optical disk libraryunit during reproduction of multimedia data recorded over plural opticaldisks, this new request for reproduction is refused if an optical diskhaving the multimedia data requested by the new request is the same asone of the plural optical disks having the multimedia data beingreproduced. Therefore, unwanted interruption in the reproduction due toa request for reproduction that exceeds the ability of the optical diskis avoided.

According to an eleventh aspect of the present invention, in a methodfor reproducing multimedia data in response to plural requests forreproduction using an optical disk library unit having at least oneoptical disk drive, the method; an upper limit of the number ofmultimedia data that can be reproduced simultaneously from a singleoptical disk is stored; a reproduction number for each optical diskcontained in the optical disk library unit is stored, which reproductionnumber is the sum of the number of multimedia data being reproduced fromthe optical disk and the number of multimedia data to be reproducedlater from the optical disk; and when a request for reproduction ofmultimedia data is given to the optical disk library unit, this requestis refused if the number obtained by adding 1 to the reproduction numberof the optical disk having the requested multimedia data exceeds theupper limit number. Therefore, unwanted interruption in the reproductiondue to a request for reproduction that exceeds the ability of theoptical disk is avoided.

According to a twelfth aspect of the present invention, a multimediaserver system comprises an optical disk library unit wherein multimediadata recorded in plural optical disks are processed with at least two,first and second, optical disk drives, and a server for distributing themultimedia data recorded in the optical disks to plural clients, andthis system is characterized by a reproduction order storage means forstoring the order of the plural optical disks to reproduce themultimedia data from the optical disks, and storing storage places ofthe optical disks in the optical disk library unit; an operating statestorage means for storing the operating state of each optical diskdrive; and a control means for controlling reading of multimedia datafrom the optical disk library unit and distribution of the multimediadata to the clients, in response to requests for reproduction ofmultimedia data from the clients. In this system, when multimedia datarecorded over some of the optical disks is requested, during reading andreproduction of the requested multimedia data from one of the opticaldisks mounted in the first optical disk drive, the control means takesthe next optical disk having the requested data from the storage placeaccording to the content of the reproduction order storage means. Then,the control means mounts the next optical disk in the second opticaldisk drive that is judged as usable according to content of theoperating state storage means, and starts reading and reproduction ofmultimedia data from the next optical disk immediately after the readingfrom the optical disk in the first optical disk drive is completed.Therefore, it is possible to continuously reproduce the multimedia datawithout interruption due to exchange of the optical disks.

According to a thirteenth aspect of the present invention, a multimediaserver system comprises an optical disk library unit wherein multimediadata recorded in plural optical disks are processed with at least two,first and second, optical disk drives, and a server for distributing themultimedia data recorded in the optical disks to plural clients, and thesystem is characterized by a reproduction order storage means forstoring the order of the plural optical disks to reproduce themultimedia data from the optical disks, and storing storage places ofthe optical disks in the optical disk library unit; a reproduction timestorage means for storing the time required for reproduction ofmultimedia data from each optical disk; an exchange time storage meansfor storing the time required for exchange of the optical disks; areservation data storage means for storing, for each optical disk havingmultimedia data requested by the client, an optical disk drive to beused for reproduction of the requested data, and the reservation timeobtained by adding the time required for exchange the optical disks tothe time required for the reproduction; and a control means forcontrolling reading of multimedia data from the optical disk libraryunit and distribution of the multimedia data to the clients, in responseto requests for reproduction of multimedia data from the clients. Inthis system, when a request for reproduction of multimedia data is givento the control means, the control means updates the contents of thereservation data storage means according to the request, referring tothe contents of the reproduction order storage means, the reproductiontime storage means, the exchange time storage means, and the reservationdata storage means, and then the control means controls mounting of theoptical disk having the requested data and reading and reproduction ofthe requested data. Therefore, unwanted interruption in the reproductiondue to exchange of the optical disks is avoided, and the optical diskdrive can be used with high efficiency in response to the requests fromplural clients.

According to a fourteenth aspect of the present invention, a multimediaserver system comprises an optical disk library unit wherein multimediadata recorded in plural optical disks are processed with at least oneoptical disk drive, and a server for distributing the multimedia datarecorded in the optical disks to plural clients, the system ischaracterized by an exchange time storage means for storing the timerequired for exchange of the optical disks in the optical disk libraryunit; a reproduction order storage means for storing the order of theplural optical disks to reproduce the multimedia data from the opticaldisks, and storing storage places of the optical disks in the opticaldisk library unit; a reproduction time storage means for storing thetime required for reproduction of multimedia data from each opticaldisk; a reproduction time measuring means for measuring the time duringwhich reproduction of the multimedia data is performed; a temporarystorage means for temporarily storing multimedia data read from theoptical disk; and a control means for controlling reading of multimediadata from the optical disk library unit and distribution of themultimedia data to the clients, in response to requests for reproductionof multimedia data from the clients. In this system, when multimediadata recorded over plural optical disks is requested, the control meansreads multimedia data by an amount larger than an amount equivalent tothe content of the exchange time storage means and stores the data inthe temporary storage means, during reading and reproduction of themultimedia data from one of the optical disks. When the remainingreproduction time of the optical disk, which is calculated from thecontent of the reproduction time storage means and the result ofmeasurement by the reproduction time measuring means, becomes lower thanthe content of the exchange time storage means, the control meanscontrols exchange of the optical disks according to the content of thereproduction order storage means, during reading and reproduction of thetemporarily stored multimedia data. Therefore, it is possible tocontinuously reproduce the multimedia data without interruption due toexchange of the optical disks.

According to a fifteenth aspect of the present invention, a multimediaserver system comprises an optical disk library unit wherein multimediadata recorded in plural optical disks are processed with at least oneoptical disk drive, and a server for distributing the multimedia datarecorded in the optical disks to plural clients, and this system ischaracterized by an exchange time storage means for storing the timerequired for exchange of the optical disks within the optical disklibrary unit; a data recording position storage means for storingpositions where the multimedia data are recorded in the optical disks; areading speed storage means for storing a possible reading speed of theoptical disk drive; a reproducing speed storage means for storing areading speed required for reproduction of the multimedia data; atemporary storage means for temporarily storing the multimedia data readfrom the optical disks; a control means for controlling reading ofmultimedia data from the optical disk library unit and distribution ofthe multimedia data to the clients, in response to requests forreproduction of multimedia data from the clients. In this system, whenmultimedia data recorded over some of the optical disks is requested,the control means calculates a prefetching start position on the basisof the contents of the exchange time storage means, the data recordingposition storage means, the reading speed storage means, and thereproducing speed storage means, in advance of reading and reproductionof the requested data from the optical disks. Then, the control meanscontrols prefetching of the multimedia data from the prefetching startposition and storage of the prefetched data in the temporary storagemeans, during reading and reproduction of the multimedia data. Then, thecontrol means controls reading and reproduction of the multimedia datastored in the temporary storage means when the optical disk in the diskdrive is exchanged for another optical disk. Therefore, it is possibleto continuously reproduce the multimedia data without interruption dueto exchange of the optical disks.

According to a sixteenth aspect of the present invention, a multimediaserver system comprises an optical disk library unit wherein multimediadata recorded in plural optical disks are processed with at least oneoptical disk drive, and a server for distributing the multimedia datarecorded in the optical disks to plural clients, the system ischaracterized by a recording media storage means for storing, for eachmultimedia data, an identification data that shows an optical disk inwhich the multimedia data is recorded; an identification data comparingmeans for comparing the identification data of the plural optical diskswith each other; and a control means for accepting or refusing a requestfor reproduction of multimedia data from the client, on the basis of theresult of the comparison by the identification data comparing means.Since the data transmitting ability of the system is compared with thedata transmitting speed required for continuous reproduction and arequest for reproduction that exceeds the ability is refused, unwantedinterruption in the reproduction is avoided.

According to a seventeenth aspect of the present invention, a multimediaserver system comprises an optical disk library unit wherein multimediadata recorded in plural optical disks are processed with at least oneoptical disk drive, and a server for distributing the multimedia datarecorded in the optical disks to plural clients, the system ischaracterized by a reproducible data number storage means for storing anupper limit of the number of multimedia data that can be reproducedsimultaneously from each optical disk; a reproduction number storagemeans for storing a reproduction number of each optical disk, whichreproduction number is the sum of the number of multimedia data beingreproduced from the optical disk and the number of multimedia data to bereproduced later from the optical disk; and a control means foraccepting or refusing a request for reproduction of multimedia data fromthe client, on the basis of the contents of the reproducible data numberstorage means and the reproduction number storage means. Since the datatransmitting ability of the system is compared with the datatransmitting speed required for continuous reproduction and a requestfor reproduction that exceeds the ability is refused, unwantedinterruption in the reproduction is avoided.

According to an eighteenth aspect of the present invention, theabove-described multimedia server system further comprises a recordingmedia storage means for storing, for each multimedia data, anidentification data that shows an optical disk in which the multimediadata is recorded; and an identification data comparing means forcomparing the identification data of the plural optical disks with eachother; and the control means accepts or refuses the request forreproduction of multimedia data from the client, on the basis of theresult of the comparison by the identification data comparing means.

According to a nineteenth aspect of the present invention, theabove-described multimedia server system further comprises areproducible data number storage means for storing an upper limit of thenumber of multimedia data that can be reproduced simultaneously fromeach optical disk; and a reproduction number storage means for storing areproduction number of each optical disk, which reproduction number isthe sum of the number of multimedia data being reproduced from theoptical disk and the number of multimedia data to be reproduced laterfrom the optical disk; and the control means accepts or refuses therequest for reproduction of multimedia data from the client, on thebasis of the contents of the reproducible data number storage means andthe reproduction number storage means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a multimedia server systemaccording to a first embodiment of the invention.

FIGS. 2(a) and 2(b) are block diagrams illustrating hardware structuresof a server and a client, respectively, in the multimedia server systemaccording to the first embodiment of the invention.

FIG. 3 is a block diagram illustrating a server unit according to thefirst embodiment of the invention.

FIG. 4 is a block diagram illustrating a client according to the firstembodiment of the invention.

FIGS. 5(a)-5(c) are tables showing data structures stored in storagemeans in the server unit according to the first embodiment of theinvention.

FIG. 6 is a flowchart illustrating the operation of the multimediaserver system according to the first embodiment of the invention.

FIGS. 7(a)-7(d) are tables illustrating specific data stored in thestorage means in the server unit according to the first embodiment ofthe invention.

FIG. 8 is a block diagram illustrating a server unit according to asecond embodiment of the invention.

FIGS. 9(a)-9(c) are tables showing data structures stored in storagemeans in the server unit according to the second embodiment of theinvention.

FIG. 10 is a flowchart illustrating the operation of a multimedia serversystem according to the second embodiment of the invention.

FIGS. 11(a)-11(d) are tables illustrating specific data stored in thestorage means in the server unit according to the second embodiment ofthe invention.

FIG. 12 is a block diagram illustrating a server unit according to athird embodiment of the invention.

FIG. 13 is a flowchart illustrating the operation of a multimedia serversystem according to the third embodiment of the invention.

FIG. 14 is a flowchart illustrating the operation of a multimedia serversystem according to a fourth embodiment of the invention.

FIG. 15 is a schematic diagram illustrating an optical disk library unitaccording to the fourth embodiment of the invention.

FIG. 16 is a block diagram illustrating a server unit according to asixth embodiment of the invention.

FIG. 17(a) is a table showing a data structure stored in a storage meansin the server unit according to the sixth embodiment, and FIG. 17(b) isa table showing specific data stored in the storage means.

FIG. 18 is a flowchart illustrating the operation of a multimedia serversystem according to the sixth embodiment of the invention.

FIGS. 19(a) and 19(b) are diagrams for explaining jumping reproductionaccording to a seventh embodiment of the invention.

FIG. 20 is a block diagram illustrating a server unit according to aneighth embodiment of the invention.

FIG. 21(a) is a table showing a data structure stored in a storage meansin the server unit according to the eighth embodiment of the invention,and FIG. 21(b) is a table showing specific data stored in the storagemeans.

FIG. 22 is a block diagram illustrating a server unit according to aninth embodiment of the invention.

FIG. 23(a) is a table showing a data structure stored in a storage meansin the server unit according to the ninth embodiment of the invention,and FIG. 23(b) is a table showing specific data stored in the storagemeans.

FIG. 24 is a block diagram illustrating a hardware structure of amultimedia data reproducing apparatus according to tenth and eleventhembodiments of the invention.

FIG. 25 is a block diagram illustrating the multimedia data reproducingapparatus according to the tenth embodiment of the invention.

FIG. 26 is a block diagram illustrating the multimedia data reproducingapparatus according to the eleventh embodiment of the invention.

FIG. 27 is a block diagram illustrating a multimedia server systemaccording to the prior art.

FIG. 28 is a schematic diagram illustrating an optical disk library unitincluded in the prior art multimedia server system.

FIG. 29 is a block diagram illustrating a server unit according to theprior art.

FIG. 30 is a block diagram illustrating a client according to the priorart.

FIG. 31(a) is a table showing a data structure stored in a storage meansin the prior art server unit, and FIG. 31(b) is a table showing specificdata stored in the storage means.

FIG. 32 is a flowchart showing the operation of the prior art multimediaserver system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

In a multimedia server system according to a first embodiment of theinvention, when multimedia data recorded over plural optical disks isreproduced successively, in advance of exchange of the optical disks,the next optical disk is mounted in a disk drive.

FIG. 1 is a block diagram illustrating a multimedia server systemaccording to the first embodiment of the invention. Since functions ofan optical disk library unit 500, a server unit 100, clients 700, 701,702, . . . , a network 650, and a connection 550 shown in FIG. 1 areidentical to those already described for the prior art system, repeateddescription is not necessary. In this system, the server unit 100 andthe optical disk library unit 500 serve as a video server thatdistributes multimedia data to plural clients through the network 650.The structure of the library unit 500 is the same as the prior artlibrary unit shown in FIG. 28.

FIG. 2(a) is a block diagram illustrating the hardware structure of thevideo server comprising the server unit and the optical disk libraryunit. In the figure, reference numeral 201 designates an input/outputunit (hereinafter referred to as I/O unit) for inputting various setpoints and outputting the operating state of the video server, such as"under operation" or "malfunction". The I/O unit 201 is implemented byan input means, such as a keyboard or a mouse, and an output means, suchas a display unit. Reference numeral 202 designates a real time clock toknow the time in the video server. A network I/F 203 is a circuit forcontrolling transmission and reception of data through the network. ACPU (Central Processing Unit) 204 executes an operating system (OS) ofthe video server, and a control program for reproduction of multimediadata. A main storage unit 205 stores the operating system of the videoserver, the control program for reproduction of multimedia data, anddata used for the control. A disk I/F 206 is a disk control circuit fordirecting a magnetic disk drive 207 and the optical disk library unit500 to read or write data, according the SCSI standard or the like. Themagnetic disk drive 207 is used for recording the operating system ofthe video server and the control program for reproduction of multimediadata, and for saving the data stored in the main storage unit 205.

FIG. 2(b) is a block diagram illustrating a hardware structure of aclient. A display unit 208 shows multimedia data, and a speaker is usedas the display unit when voice data is included. A display I/F 209 is acircuit for controlling the display of multimedia data on the displayunit 208. A user inputs a request for reproduction of desired multimediadata to the client, using an input unit 210, such as a keyboard or amouse. An MPEG decoder 211 expands multimedia data compressed by MPEG sothat the data can be displayed on the display unit 208. A network I/F212 is a circuit for controlling transmission and reception of datathrough the network. A CPU 213 executes an operating system (OS) of theclient and a control program for reproduction of multimedia data. Mainstorage unit 214 stores the operating system of the client and thecontrol program for reproduction of multimedia data. A real time clock215 is similar to the real time clock 202 in the server unit. A disk I/F216 is a disk control circuit for directing a magnetic disk drive 217 toread or write data. The magnetic disk drive 217 is used for recordingthe operating system of the client and the control program forreproduction of multimedia data.

FIG. 3 is a block diagram illustrating the server unit 100 viewed fromits function. In FIG. 3, a library control means 101 is implemented bythe disk I/F 206 shown in FIG. 2(a) and the control program, and outputsan instruction to control the optical disk library unit 500. A controlmeans 102 is implemented by the CPU 204, the main storage unit 205,which are shown in FIG. 2(a), and the control program for reproductionof multimedia data. The control means 102 includes means for readingmultimedia data from an optical disk and controls reading andtransmission of multimedia data in response to a request from theclient. A data transmitting and receiving means 103 is implemented bythe network I/F 203 shown in FIG. 2(a) and the control program, andexchanges data with the client through the network 650. A operatingstate storage means 104 is implemented by the main storage unit 205 andthe magnetic disk drive 207 shown in FIG. 2(a), and stores the operatingstate of the optical disk drive in the optical disk library unit 500. Areproduction order storage means 105 is implemented by the main storageunit 205 and the magnetic disk drive 207 shown in FIG. 2(a), and storesthe order of optical disks to be reproduced when desired multimedia datais recorded over plural optical disks. A reproduction time storage means106 is implemented by the main storage unit 205 and the magnetic diskdrive 207 shown in FIG. 2(a), and stores the time required forreproduction of multimedia data. An exchange time storage means 109 isimplemented by the main storage unit 205 and the magnetic disk drive 207shown in FIG. 2(a), and stores the time required for exchange of theoptical disks in the optical disk drive in the library unit 500.

FIG. 4 is a block diagram illustrating the client 700 viewed from itsfunction. In FIG. 4, a reproduction request accepting means 706 isimplemented by the input unit 210 and the display unit 208 shown in FIG.2(b) and the control program for reproduction of multimedia data, andthis means 706 accepts a request for reproduction of multimedia datafrom a user. A data reproducing means 707 is implemented by the MPEGdecoder 211 and the display I/F shown in FIG. 2(b) and the controlprogram for reproduction of multimedia data. This means 707 expandsmultimedia data compressed by MPEG so that the data can be displayed onthe display unit 208, reproduces the data, and displays the data on thedisplay unit 703. A data transmitting and receiving means 704 isimplemented by the network I/F 203 shown in FIG. 2(b) and the controlprogram, and exchanges data or requests with the server unit 100 throughthe network 650. A reproduction time measuring means 705 is complementedby the real time clock 215 shown in FIG. 2(b). When multimedia data isreproduced, the measuring means 705 measures the time required for thereproduction and transmits the result of the measurement, through thedata transmitting and receiving means 704 and the network 650, to thecontrol means 102 of the server unit 100.

FIGS. 5(a) to 5(c) show data structures recorded in the operating statestorage means 104, the reproduction order storage means 105, and thereproduction time storage means 106, respectively. The operating statestorage means 104 stores the present state of each optical disk drive inthe library unit 500, and the identification number of the optical diskmounted in the optical disk drive. The data stored in the operatingstate storage means 104 are updated by the control means 102 for eachoperation of the optical disk drive. The reproduction order storagemeans 105 stores the title of multimedia data, the number of opticaldisks over which the multimedia data is recorded, the order of theoptical disks to reproduce the multimedia data, the identificationnumber of each optical disk, and the storage position of each opticaldisk. The reproduction time storage means 106 stores the time requiredfor reproduction of the multimedia data.

FIG. 6 is a flowchart illustrating the operation of the multimediaserver system according to the first embodiment of the invention whenmultimedia data recorded over plural optical disks is reproduced.

It is assumed that two optical disk drives, "Drive0" and "Drive1", arecontained in the optical disk library unit 500, and multimedia datahaving a title "multi01" is recorded over two optical disks, each forten minutes. These optical disks have identification numbers, "disk#0"and "disk#1", in the order at the recording, and the optical disks"disk#0" and "disk#1" are contained in slots #0 and #1 of the opticaldisk library unit 500, respectively. The time required for exchange ofthese disks in the library unit 500 is six seconds.

FIGS. 7(a) to 7(b) show contents stored in the operating state storagemeans 104, the reproduction order storage means 105, the reproductiontime storage means 106, and the exchange time storage means 109,respectively. Before starting reproduction, the operating state storagemeans 104 has contents shown in the first table (1. before reproduction)in FIG. 7(a), and the reproduction order storage means 105, thereproduction time storage means 106, and the exchange time storage means109 have contents shown in FIGS. 7(b), 7(c), and 7(d), respectively.

Hereinafter, the operation of the multimedia server system according tothe first embodiment of the invention will be described according to theflowchart shown in FIG. 6.

First of all, in step 1, when the reproduction request accepting means706 in the client 700 accepts a request for reproduction of multimediadata having the title "multi01" from the user, the data transmitting andreceiving means 704 transmits this request through the network 650 tothe data transmitting and receiving means 103 in the server unit 100.Then, the data transmitting and receiving means 103 transmits therequest to the control means 102. Receiving the request, the controlmeans 102 finds that the first optical disk in which multimedia datahaving the requested title "multi01" is recorded is the optical disk"disk#0" whose reproduction order is "1", and this disk is contained inthe slot #0, in reference to the contents of the reproduction orderstorage means 105 shown in FIG. 7(b). Then, from the contents of theoperating state storage means 104 shown in the first table (1. beforereproduction) in FIG. 7(a), the control means 102 finds that both theoptical disk drives "Drive0" and "Drive1" stand by, i.e., no opticaldisk is mounted in these drives.

Thereafter, control means 102 operates the conveyer 504 in the opticaldisk library unit 500, through the library control means 101 and thecontroller 505 in the optical disk library unit 500, so that theconveyer 504 takes the optical disk "disk#0" from the slot #0 of thestorage shelf 502 and inserts the disk in the optical disk drive"Drive0" which is in the "stand-by" state, i.e., in which drive no diskis mounted. The operation of the optical disk library unit is similar tothat described for the prior art unit. Thereafter, the control means 102updates the contents of the operating state storage means 104, as shownin the second table (2. after step 1) in FIG. 7(a).

In step 2, the control means 102 finds that the total time required forreproduction of the multimedia data "multi01" is twenty minutes, fromthe contents of the reproduction time storage means 106 shown in FIG.7(c), and judges whether or not the reproduction of the multimedia data"multi01" is completed by comparing the time required for thereproduction, i.e., twenty minutes, with the reproduction time measuredby the reproduction time measuring means 705 in the client 700. When thejudgment is that the reproduction is not completed, the control means102 proceeds to step 3.

In step 3, the target multimedia data "multi01" is read from the opticaldisk "disk#0" in the optical disk drive "Drive0". In step 4, the controlmeans 102 judges whether the data equivalent to the time required forreproduction of the target data from the disk "disk#0" (ten minutes) hasbeen read from the optical disk "disk#0". Since the reproduction hasjust started in this stage, it is judged that the data equivalent to tenminutes has not been completely read yet, followed by step 5.

In step 5, the control means 102 calculates the time required forreproduction of the target data remaining in the optical disk "disk#0"by subtracting the present reproduction time from the time required forreproduction of the target data from the optical disk "disk#0" (tenminutes), on the basis of the reproduction time measured by thereproduction time measuring means 705 and the contents of thereproduction time storage means 106. Then, the control means 102compares the time required for exchange of disks, which is stored in theexchange time storage means 109, with the remaining reproduction time.Since the reproduction has just started and the remaining reproductiontime is longer then the disk exchange time, the control means 102proceeds to step 6.

In step 6, the control means 102 checks the operating state storagemeans 104 and the reproduction order storage means 105 to judge whethera set-up for reproduction of the next optical disk "disk#1" is done.Since the contents of the operating state storage means 104 are as shownin the second table (2. after step 1) in FIG. 7(a), the control means102 judges that the next optical disk "disk#1" is not yet mounted in theoptical disk drive, followed by step 7.

In step 7, the control means 102 checks the stand-by optical diskdrives, i.e., drives in which optical disks are not mounted, accordingto the contents of the operating state storage means 104, and finds"Drive1". Then, the control means proceeds to step 9.

In step 9, the control means 102 instructs the conveyer 504 in thelibrary unit 500 to take the optical disk "disk#1" from the slot #1 ofthe storage shelf 502 and insert the disk in the stand-by optical diskdrive "Drive1". Thereafter, the control means 102 updates the contentsof the operating state storage means 104, as shown in the third table(3. after step 9) in FIG. 7(a).

Step 10 is executed to reproduce the target multimedia data. Morespecifically, the data read from the optical disk "disk#0" in theoptical disk drive "Drive0" is transmitted from the data transmittingand receiving means 103 in the server unit 100, through the network 650,to the data transmitting and receiving means 704 in the client 700.Then, the compressed data is expanded by the MPEG decoder in thereproducing means 707 and displayed on the display unit 703.

After step 10, the control means 102 returns to step 2. As long as thejudgment in step 5 is that the time required for reproduction of thedata remaining in the optical disk "disk#0" is longer than the diskexchange time (six seconds), steps 2, 3, 4, 5, 6, and 10 are repeated tocontinue the reproduction.

When the control means 102 judges, in step 5, that the remainingreproduction time is shorter than the disk exchange time, the controlmeans 102 proceeds to step 10. Thereafter, steps 2, 3, 4, 5, and 10 arerepeated until the control means 102 judges, in step 4, that the readingof the target data is completed. When it is judged in step 4 that thereading of the target data from the optical disk "disk#0" is completed,the control means 102 proceeds to step 8.

In step 8, in reference to the contents of the reproduction orderstorage means 105, the control means 102 controls the conveyer 504 inthe optical disk library unit 500, through the library control means101, so that the conveyer 504 returns the optical disk "disk#0", forwhich reading of the target data has just finished, to the slot #0 ofthe storage shelf 502. Then, in reference to the contents of theoperating state storage means 104, the control means 102 finds that theoptical disk "disk#1" to be reproduced next is inserted in the opticaldisk drive "Drive1", and starts the drive "Drive1". The control means102 updates the contents of the operating state storage means 104 asshown in the fourth table (4. after step 8) in FIG. 7(a).

Step 10 is executed to continue the reproduction of the targetmultimedia data. The multimedia data read from the optical disk "disk#0"in the last step 3 is transmitted from the data transmitting andreceiving means 103 in the server unit 100, through the network 650, tothe data transmitting and receiving means 704 in the client 700. Then,the compressed data is expanded by the MPEG decoder in the reproducingmeans 707 and displayed on the display unit 703.

In step 2, the control means 102 judges that the reproduction of themultimedia data "multi01" is not completed yet by comparing the contentsof the reproduction time storage means 106 with the reproduction timemeasured by the reproduction time measuring means 705, followed by step3.

In step 3, the target multimedia data "multi01" is read from the opticaldisk "disk#1" mounted in the optical disk drive "Drive1". In step 4, thecontrol means 102 judges whether reading of the target data equivalentto the time required for reproduction of the data from the optical disk"disk#1" is completed. Since the reproduction has just started, thecontrol means 102 judges that the reading is not completed yet, andproceeds to step 5.

In step 5, the time required for reproduction of the data remaining inthe optical disk "disk#1" is calculated, and this time is compared withthe time required for exchange of the optical disks. When the remainingreproduction time is longer than the disk exchange time, the controlmeans 102 proceeds to step 6.

In step 6, the control means 102 checks the reproduction order storagemeans 105 and finds that no optical disk follows. Since it is notnecessary to prepare the next optical disk, step 10 is executed.Thereafter, similar process steps are continued until the reproductionof the multimedia data "multi01" from the optical disk "disk#1" iscompleted.

As described above, in the multimedia server system according to thefirst embodiment of the invention, the server unit is equipped with thecontrol means, the reproduction order storage means providing the orderof the optical disks to be reproduced, and the operating state storagemeans providing the states of the optical disk drives. The control meanscontrols the optical disk library unit according to the reproductionorder of the disks and the operating states of the drives so that theoptical disk to be reproduced next is mounted in a free optical diskdrive in advance. Hence, reading of multimedia data from the nextoptical disk can be started immediately after reading of multimedia datafrom the previous optical disk is ended. Accordingly, when multimediadata recorded over plural optical disks is reproduced, unwantedinterruption due to exchange of disks is avoided. As a result,reproduction of multimedia data is smoothly carried out.

Embodiment 2

In a multimedia server system according to a second embodiment of theinvention, when multimedia data recorded over plural optical disks isreproduced, optical disk drives used for the reproduction are reservedin advance.

The structure of the server system, the hardware structures of theserver and the client, the structure of the client, and the structure ofthe library unit according to this second embodiment are identical tothose according to the first embodiment and, therefore, FIGS. 1, 2(a),2(b), 4, and 28 are used to explain the second embodiment.

FIG. 8 is a block diagram illustrating a server unit 100 according tothe second embodiment of the invention. In the figure, the samereference numerals as those shown in FIG. 3 designate the same orcorresponding parts. Reference numeral 108 designates a reservation datastorage means 108, and reference numeral 110 designates a clock. Thereservation data storage means 108 is implemented by the main storageunit 205 and the magnetic disk drive 207 shown in FIG. 2(a), and storesan optical disk to be reproduced, an optical disk drive used forreproduction, the reproduction time, and the reservation time. The clock110 is implemented by the real time clock shown in FIG. 2(a) and thecontrol program, and shows the present time.

FIGS. 9(a) to 9(c) show data structures stored in the reservation datastorage means 108, the reproduction order storage means 105, and thereproduction time storage means 106, respectively. The reservation datastorage means 108 stores data showing the state of reservation for anoptical disk drive. More specifically, as shown in FIG. 9(a), it stores,the identification number of an optical disk to be reproduced, thenumber of an optical disk drive used for the reproduction, thereproduction time required for the reproduction, and the reservationtime obtained by adding the disk exchange time to the reproduction time.The data structures in the reproduction order storage means 105 and thereproduction time storage means 106 shown in FIGS. 9(b) and 9(c),respectively, are similar to those described for the first embodiment.

FIG. 10 is a flowchart for explaining the operation of the multimediaserver system according to the second embodiment of the invention. FIGS.11(a) to 11(d) are tables illustrating specific data stored in therespective storage means.

As in the first embodiment of the invention, it is assumed that twooptical disk drives, "Drive0" and "Drive1", are contained in the opticaldisk library unit 500, and multimedia data having a title "multi01" isrecorded over two optical disks, each for ten minutes. Theidentification numbers of these two optical disks are, respectively,"disk#0" and "disk#1" in the order of the recording. Further, theseoptical disks "disk#0" and "disk#1" are contained in slots #0 and #1 inthe optical disk library unit 500, respectively. Furthermore,.multimedia data having a title "multi02" is recorded over two opticaldisks "disk#13" and "disk#14", and these optical disks are contained inslots #3 and #4 in the library unit 500, respectively. The multimediadata "multi02" is divided into two parts, each for nine minutes andfifty seconds, and recorded in the optical disks "disk#13" and "disk#14"in this order. The time required for exchange of disks in the libraryunit 500 is six seconds.

Before starting reproduction, the reservation data storage means 108have data shown in the first table (1. before reservation) in FIG.11(a). The reproduction order storage means 105, the reproduction timestorage means 106, and the exchange time storage means 109 have datashown in FIGS. 11(b), 11(c), and 11(d), respectively.

Hereinafter, the operation of the multimedia server system according tothe second embodiment will be described using the flowchart shown inFIG. 10.

As described for the first embodiment of the invention, a request forreproduction of multimedia data "multi01" is accepted by the client 700and transmitted to the server unit 100.

In step 1, the control means 102 checks the present time with the clock110. The present time is 12:59:00. Then, the control means 102 checksthe contents of the reservation data storage means 108. As shown in thefirst table (1. before reservation) in FIG. 11(a), the optical diskdrives "Drive0" and "Drive1" are already reserved for 12:59:54-13:09:50and 13:09:44-13:19:40, respectively, to reproduce the multimedia data"multi02".

Therefore, in order to reproduce the multimedia data "multi01" duringperiods of time other than mentioned above, the control means 102 checksthe data relating to "multi01" from the contents of the reproductionorder storage means 105 and the reproduction time storage means 106shown in FIGS. 11(b) and 11(c), respectively. Further, the control means102 checks the exchange time storage means 109, and adds the timerequired for exchange of the disks, i.e., six seconds, to the timerequired for reproduction of the data "multi01" in each optical disk,i.e., ten minutes.

Then, the control means 102 calculates a reservable period of time ineach optical disk drive, and decides that the optical disk drive"Drive0" can be reserved for 13:09:54-13:20:00 and the optical diskdrive "Drive1" can be reserved for 13:19:54-13:30:00. Then, the controlmeans 102 stores, in the reservation data storage means 108, the opticaldisks, the reserved optical disk drives, the reproduction time for eachdisk, and the reservation time for each drive, as shown in the secondtable (2. after reservation) in FIG. 11(a).

Next, the control means 102 checks the clock 110 at constant timeintervals, and mounts the first optical disk "disk#0" having themultimedia data "multi01" in the optical disk drive "Drive0".

Thereafter, steps 2 to 4 are executed as already described for the firstembodiment, followed by step 5. In step 5, the control means 102 findsthat the present time is 13:19:54, and compares the present time withthe reservation time stored in the reservation data storage means 108.When the present time has not reached the reservation time, the controlmeans 102 judges that it is not time to mount the next optical disk, sothe control means 102 proceeds to step 8. In step 8, the multimedia datais reproduced as described for step 10 according to the firstembodiment, followed by steps 2 to 4. Until it is judged in step 5 thattime to start mounting of the next optical disk is reached, theabove-mentioned process steps are repeated.

When it is judged in step 5 that time to start mounting of the nextoptical disk "disk#1" is reached, the control means 102 proceeds to step6.

In step 6, the control means 102 checks the contents of the reservationdata storage means 108 and controls the library unit 500 through thelibrary control means 101 to mount the next optical disk "diski1" in thereserved optical disk drive "Drive1", followed by step 8. In step 8,reproduction of the multimedia data recorded in the optical disk"disk#1" is performed. Thereafter, process steps similar to thosedescribed for the first embodiment are repeated.

As described above, in the multimedia server system according to thesecond embodiment of the invention, the server unit is equipped with thereservation data storage means and, before starting reproduction, thecontrol means reserves an optical disk drive for a prescribed period oftime including the time required for exchange of optical disks,according to the contents of the respective storage means, so that thedata reproduction time is not interrupted between the respective opticaldisk drives. In this way, the operation of each optical disk drive iscontrolled with time. Therefore, when multimedia data recorded overplural optical disks is reproduced, unwanted interruption inreproduction due to exchange of the disks is avoided, whereby smoothreproduction of the multimedia data is realized. Further, the opticaldisk drives in the library unit can be used with high efficiency inresponse to requests of plural clients.

Embodiment 3

In a multimedia server system according to a third embodiment of theinvention, when multimedia data recorded over plural optical disks isrecorded, a portion of the data equivalent to the time required forexchange of the disks is temporarily stored in advance, and the storeddata is reproduced when the disks are exchanged.

The multimedia server system according to this third embodiment isidentical to the multimedia server system according to the firstembodiment in the structure of the server system, the hardwarestructures of the server and the client, the structure of the client,and the structure of the library unit and, therefore, FIGS. 1, 2(a),2(b), 4, and 28 are used to explain the third embodiment.

FIG. 12 is a block diagram illustrating a server unit 100 according tothe third embodiment of the invention. In FIG. 12, the same referencenumerals as those shown in FIG. 3 designate the same or correspondingparts. A temporary storage means 111 is implemented by the main storageunit 205 and the magnetic disk unit 207 shown in FIG. 2(a), andtemporarily stores multimedia data read from the optical disk in thelibrary unit. The control means 102 includes means for prefetching themultimedia data, in addition to the data reading means.

FIG. 13 is a flowchart for explaining the operation of the multimediaserver system according to the third embodiment of the invention.

In the optical disk library unit 500, the optical disk drives, therecording condition of multimedia data "multi01", and the time requiredfor exchange of optical disks are identical to those described for thefirst embodiment of the invention. Further, in the server unit 100, thereproduction order storage means 103, the reproduction time storagemeans 104, and the exchange time storage means 109 store the same dataas shown in FIGS. 7(b), 7(c), and 7(d), respectively.

Hereinafter, the operation of the multimedia server system according tothis third embodiment will be described using the flowchart shown inFIG. 13.

When a request for multimedia data "multi01" is accepted by the client700, this request is transmitted to the server unit 100, and steps 1 and2 are executed in the same manner as described for steps 1 and 2according to the first embodiment, followed by step 3.

In step 3, the control means 102 reads the multimedia data "multi01"from the optical disk "disk#0" mounted in the optical disk drive"Drive0". Next, in step 4, since the reproduction time storage means 106stores the data shown in FIG. 7(c) and the exchange time storage means109 stores the data shown in FIG. 7(d), the control means 102 finds thatthe time required for reproduction of the multimedia data "multi01" inthe optical disk "disk#0" is ten minutes and the time required forexchange of the optical disks is six seconds. According to these data,the control means 102 decides that a portion of the multimedia data"multi01" within a range from nine minutes and fifty-four seconds to tenminutes in the reproduction time is equivalent to the disk exchangetime. Then, the control means 102 starts reading of the data for thedisk exchange time from the optical disk "disk#0" by the prefetchingmeans, and stores the data in the temporary storage means 111.

In step 5, the control means 102 calculates the time required forreproduction of remaining multimedia data in the optical disk "disk#0",from the reproduction time obtained by the reproduction time measuringmeans 705 and the data stored in the reproduction time storage means106. Then, the control means 102 compares the remaining reproductiontime with the contents of the exchange time storage means 109 and judgeswhether the remaining reproduction time is longer than the disk exchangetime. In this stage, since the remaining reproduction time is longerthan the disk exchange time (six seconds), the control means 102proceeds to step 6. In step 6, reproduction of the multimedia data isperformed in the same manner as described for step 10 according to thefirst embodiment, followed by step 2.

Until the control means 102 judges in step 5 that the remainingreproduction time for the multimedia data "multi01" recorded in theoptical disk "disk#0" becomes equal to or shorter than the disk exchangetime, steps 2 to 6 are repeated.

When it is judged in step 5 that the remaining reproduction time isequal to the disk exchange time, step 7 is executed. In step 7, thecontrol means 102 reads the multimedia data "multi01" which is stored inthe temporary storage means 111.

Next, in step 8, the control means 102 checks whether the next opticaldisk is prepared, according to the contents of the operating statestorage means 104. In this stage, since the next optical disk is notprepared, the control means 102 proceeds to step 9.

In step 9, the control means 102 finds that the next optical disk is"disk#1" and this disk is contained in the slot #1, according to thecontents of the reproduction order storage means 105. Then, the controlmeans 102 controls the library unit 500 through the library controlmeans 101 so that the optical disk "disk#1" is taken out of the slot #1of the storage shelf and inserted in the optical disk drive "Drive1".Then, the control means 102 updates the contents of the operating statestorage means 104.

Next, in step 10, the control means 102 transmits the multimedia dataread from the temporary storage means 111, through the data transmittingand receiving means 103 and the network 650, to the client 700. Thetransmitted multimedia data is reproduced in the client 700.

In step 11, the control means 102 judges whether or not the reproductionof the multimedia data stored in the temporary storage means 111 isended, by comparing the reproduction time measured by the reproductiontime measuring means 705 with the contents of the reproduction timestorage means 106. When the reproduction time does not reach the timerequired for the reproduction, the control means 102 Judges that thereproduction is not ended yet and proceeds to step 5.

Until it is judged in step 11 that the reproduction of the multimediadata stored in the temporary storage means 111 is ended, steps 5, 7, 8,10, and 11 are repeated.

In step 8, the control means 102 Judges that the next optical disk isprepared, step 8 is followed by step 10. When it is judged in step 11that the reproduction of the multimedia data stored in the temporarystorage means 111 is ended, the control means 102 proceeds to step 12.In step 12, the control means 102 erases the multimedia data stored inthe temporary storage means 111.

Thereafter, the control means 102 returns to step 2. In step 2, thecontrol means 102 judges that the reproduction of the multimedia data"multi01" is not ended and proceeds to step 3. In step 3, the controlmeans 102 controls the library control means 10 so that the multimediadata "multi01" is read from the optical disk "disk#1". The reading andreproduction of the multimedia data "multi01" from the optical disk"disk#1" are continued until the end of the reproduction.

As described above, in the multimedia server system according to thethird embodiment of the invention, the server unit is equipped with thetemporary storage means, and a portion of multimedia data equivalent tothe disk exchange time is stored in the temporary storage means whenreading of the multimedia data from the optical disk is started. Then,the control means exchanges the optical disk in the optical disk drivefor the next optical disk during reproduction of the multimedia datastored in the temporary storage means. Therefore, reading of themultimedia data from the next optical disk can be started immediatelyafter reading of the multimedia data from the temporary storage means iscompleted. As a result, when multimedia data recorded over pluraloptical disks is reproduced, unwanted interruption of the reproductionis avoided.

Embodiment 4

In a multimedia server system according to a fourth embodiment of theinvention, when multimedia data recorded over plural optical disks isreproduced, a portion of the multimedia data, which is read out at aspeed higher than a speed required for reproduction of the multimediadata, is stored temporarily and then transmitted.

Since the structure of the multimedia server system and the recordingstate of the multimedia data according to this fourth embodiment areidentical to those already described for the third embodiment, repeateddescription is not necessary. Further, the optical disk drives in theoptical disk library unit 500, the recording state of multimedia data"multi01", and the time required for exchange of optical disks areidentical to those described for the first embodiment. In the serverunit 100, the contents of the reproduction order storage means 105, thereproduction time storage means 106, and the exchange time storage means109 are identical to those mentioned for the first embodiment, so thatFIGS. 7(b), 7(c), and 7(d) are used for the description. Furthermore, itis assumed that a data reading speed of 150 KBytes/sec is required forreproduction of multimedia data "multi01".

FIG. 14 is a flowchart for explaining the operation of the multimediaserver system according to the fourth embodiment of the invention.

In FIG. 14, steps 1 and 2 are executed in the same manner as steps 1 and2 according to the third embodiment. In step 3, the control means 102decides a reading speed on the basis of the above-mentioned readingspeed required for reproduction, i.e., 150 KBytes/sec, the reproductiontime obtained from the contents of the reproduction time storage means106, i.e., ten minutes (10*60 seconds), and the disk exchange timeobtained from the contents of the exchange time storage means 109, i.e.,six seconds, according to the following formula.

    ______________________________________    reading speed ≧    reading speed required for reproduction *    reproduction time/(reproduction time - disk exchange time)    ______________________________________

Therefore,

    ______________________________________    reading speed ≧    150 (KBytes/sec) * (10 * 60)(sec)/(10 * 60 - 6)(sec) =    151.5 (KBytes/sec)    ______________________________________

The control means 102 decides that the reading speed is 640 KBytes/sec,reads the multimedia data from the optical disk "disk#0" at this speed,and stores the data in the temporary storage means 111.

Step 4 is executed in the same manner as step 5 according to the thirdembodiment, followed by step 5. In step 5, the data transmitting andreceiving means 103 transmits the multimedia data stored in thetemporary storage means 111 in step 3 through the network 650 to theclient 700, and the multimedia data is reproduced in the client 700.Then, the control means 102 deletes the read and transmitted data fromthe temporary storage means 111, followed by step 2. Thereafter, steps 2to 5 are repeated until the remaining reproduction time becomes equal toor shorter than the time required for exchange of the optical disk, andin step 5, the data stored in the temporary storage means 111 isreproduced.

When the remaining reproduction time becomes equal to the disk exchangetime in step 4, step 6 is executed. Steps 6 to 11 are executed in thesame manner as steps 7 to 12 described for the third embodiment.Thereafter, the same process steps as mentioned for the third embodimentare executed until the end of the reproduction.

As described above, in the multimedia server system according to thefourth embodiment of the invention, the server unit is equipped with thetemporary storage means, and data which is read from the optical disk ata speed higher than the reading speed required for reproduction isstored in the temporary storage means. The data stored in the temporarystorage means is transmitted to the client and reproduced. Since thespeed for reading and temporarily storing the data is higher than thespeed for transmitting the data, when the reproduction time required forthe remaining multimedia data in the optical disk is equal to the diskexchange time, the amount of the multimedia data stored in the temporarystorage means is larger than the amount of the data equivalent to thedisk exchange time. Since the optical disk mounted in the optical diskdrive is exchanged during reproduction of the temporarily storedmultimedia data, reading of the multimedia data from the next opticaldisk can be started immediately after reading of the multimedia datafrom the temporary storage means is completed. Therefore, whenmultimedia data recorded over plural optical disks is reproduced, thereproduction can be performed continuously, without interruption due toexchange of the disks.

Embodiment 5

In a multimedia server system according to a fifth embodiment of theinvention, the storage position of the optical disk to be reproducednext, which position is stored in advance of exchange of the opticaldisks, can be changed.

The structure of the multimedia server system and the recording state ofmultimedia data according to this fifth embodiment are identical tothose mentioned for the third embodiment of the invention except thestructure of the optical disk library unit.

FIG. 15 is a schematic diagram illustrating an optical disk library unit500 according to the fifth embodiment of the invention. The library unit500 includes a storage shelf 502 that contains fifty optical disks inslots #0 to #49. Multimedia data having a title "multi01" is recordedover two disks set in slots #0 and #1, and identification numbers ofthese optical disks are "disk#0" and "disk#1", respectively. The libraryunit 500 further contains an optical disk drive 503 having a drivenumber "Drive0". The positional relationship between the optical diskdrive 503 and the respective slots of the storage shelf 502 is asfollows. That is, the slot #0 is most distant from the optical diskdrive 503, and the distance from the optical disk drive 503 reduces withan increase in the number of the slot. The disk exchange time is nineminutes when the disk is in the slot #0 which is most distant from thedisk drive 503 whereas it is three minutes when the disk is in the slot#49 which is nearest to the disk drive 503.

The operation of the multimedia server system according to this fifthembodiment is fundamentally identical to the operation of the systemaccording to the third or fourth embodiment except that, in step 1 ofthe flowchart shown in FIG. 13 or 14, the optical disk "disk#0" ismounted in the drive 503 and, after Judgment in step 2 and beforeexecution of step 3, the following operation is added.

That is, the control means 102 finds that an optical disk to bereproduced next is "disk#1" from the contents of the reproduction orderstorage means 105. Then, the control means 102 starts reading of themultimedia data "multi01" recorded in the optical disk "disk#0" mountedin the drive "Drive0" and, at the same time, the control means 102 takesthe next optical disk "disk#1" from the slot #1 of the storage shelf 502and exchanges an optical disk in the slot #49 which is nearest to theoptical disk drive "Drive0" for the optical disk "disk#1". After theexchange of the optical disks, the control means 102 updates the storageposition of the optical disk "disk#1" stored in the reproduction orderstorage means 105.

In the multimedia server system according to the fifth embodiment of theinvention, before exchange of the optical disks, the optical disk to bereproduced next is moved to a storage position (slot) nearest to theoptical disk drive, so that the time required for conveying the disk isreduced, resulting in a reduction in the disk exchange time. In the casementioned above, the disk exchange time is reduced by about 6 seconds.Therefore, the amount of multimedia data to be stored temporarily forthe time required to exchange the disks can be reduced. Since a highspeed but expensive recording medium, such as a memory, is usuallyemployed as means for temporarily storing the multimedia data, thereduction in the amount of the multimedia data temporarily stored in thestorage means results in a reduction in the power consumption of thestorage means, whereby continuous reproduction of multimedia data can berealized with less hardware resources, as compared to the third orfourth embodiment of the invention.

Embodiment 6

In a multimedia server system according to a sixth embodiment of thepresent invention, when multimedia data recorded over plural opticaldisks is reproduced, a portion of the multimedia data equivalent to thetime required to exchange the optical disks is temporarily stored andthen reproduced.

The structure of the multimedia server system, the hardware structuresof the server and the client, the structure of the client, and thestructure of the library unit, according to this sixth embodiment of theinvention, are identical to those described for the first embodiment ofthe invention, so that FIGS. 1, 2, 4, and 28 are used for explaining thesixth embodiment.

FIG. 16 is a block diagram illustrating a server unit 100 according tothe sixth embodiment of the invention. In the server unit 100, a librarycontrol means 101, a control means 102, a data transmitting andreceiving means 103, and an exchange time storage means 109 areidentical to those according to the first embodiment of the invention,and a temporary storage means 111 is identical to that according to thethird embodiment of the invention. Hence, descriptions for these meansare omitted. The control means 102 includes a prefetching means as inthe third embodiment of the invention.

A data recording position storage means 112 is implemented by the mainstorage unit 205 and the magnetic disk drive 207 shown in FIG. 2(a), andstores titles (file names) of multimedia data, identification numbers ofoptical disks, recording positions (logical block addresses) of themultimedia data in the optical disks, and storage positions of theoptical disks in the storage shelf 502 in the optical disk library unit500. A reading speed storage means 113 is implemented by the mainstorage unit 205 and the magnetic disk drive 207 shown in FIG. 2(a), andstores the data reading speed from the optical disk mounted in theoptical disk drive 503 in the library unit 500, as the number of logicalblocks that can be read during a unit time. A reproduction speed storagemeans 114 is implemented by the main storage unit 205 and the magneticdisk drive 207 shown in FIG. 2(a), and stores the reading speed requiredfor reproduction of the multimedia data recorded in the optical disk, asthe number of logical blocks per a unit time.

FIG. 17(a) shows a data structure in the data recording position storagemeans 104, and FIG. 17(b) shows specific data stored in the storagemeans 104. FIG. 18 is a flowchart for explaining the operation of themultimedia server system according to the sixth embodiment of theinvention.

The optical disk library unit 500 contains four optical disks. Over twooptical disks, MPEG1 multimedia data "multi01" of 8 MB, i.e., 4 MB foreach disk, is recorded. On the other hand, over three optical disks,MPEG1 multimedia data "multi02" of 12 MB, i.e., 4 MB for each disk, isrecorded. The storage positions of these optical disks in the libraryunit 500 and the recording positions of these multimedia data on theoptical disks are as shown in FIG. 17(b). The optical disk library unit500 takes eight seconds to exchange the optical disks. The performanceof the optical disk drive contained in the optical disk library unit 500is as follows: The maximum seek time is 200 ms, the maximum rotationwaiting time is 30 ms, and the minimum reading speed: 500 KBytes/sec.The network in the multimedia server system is constructed by anethernet having a maximum transmission speed of 10 Mbps (megabits persecond). Two clients are connected to the server system through thenetwork. The reproduction bit rate of MPEG 1 is 1.5 Mbps (about 187KBytes/sec). The logical block size of each optical disk is 512 bytes.

Hereinafter, the operation of the multimedia server system according tothis sixth embodiment will be described using the flowchart shown inFIG. 18.

Initially, in step 1, by the control means 102, the minimum readingspeed of the optical disk drive, 500 KBytes/sec, is stored in thereading speed storage means 113, the MPEG 1 reproduction bit rate, 1.5Mbps (about 187 KBytes/sec), is stored in the reproduction speed storagemeans 114, and the optical disk exchange time, eight seconds, is storedin the optical disk exchange time storage means 109.

Next, in step 2, the control means 102 receives. a request forreproduction of multimedia data "multi01" from the client 700, throughthe network 650 and the data transmitting and receiving means 103.

In step 3, from the contents of the data recording position storagemeans 104 shown in FIG. 17(b), the control means 102 finds that themultimedia data "multi01" requested by the client 700 is recorded overthe optical disks "disk#1" and "disk#3", and these optical disks arerespectively stored in slots #10 and #12 of the storage shelf 502 in theoptical disk library unit 500.

In step 4, the control means 102 performs the following calculations.

Initially, the control means 102 calculates the amount of multimediadata to be reproduced during the disk exchange time, as the number oflogical blocks on the optical disk.

    ______________________________________    the number of logical blocks required for reproduction    (blocks) =    reproduction speed (Bytes/sec) * disk exchange time    (sec)/logical black size (Bytes/block) =    (187 * 1024) * 8/512 =    2992 (blocks)    ______________________________________

Next, the control means 102 calculates the prefetching speed of datathat can be prefetched in parallel with reading and reproduction, as thenumber of logical blocks per a unit time. That is, the prefetching speedis a difference between the reading speed and the reproduction speed.Since the minimum reading speed of the optical disk drive 503 is 500KBytes/sec and the required reproduction speed of MPEG1 is 1.5 Mbps (187KByte/sec),

    ______________________________________    the number of prefetchable logical blocks per a unit    time (blocks/sec) =    (reading speed - reproduction speed) (Bytes/sec)/    logical block size (Bytes/block) =    (500 - 187) * 1024/512 =    626 (blocks/sec)    ______________________________________

Next, on the basis of the results of the above-mentioned calculations, areading time of multimedia data required for reproduction duringexchange of the optical disks is obtained.

    ______________________________________    prefetching time (sec) =    the number of logical blocks required for    reproduction (blocks)/the number cf prefetchable logical    blocks per a unit time (blocks/sec) =    2992/626 =    4.77 (sec)    ______________________________________

From this result, the number of logical blocks to be prefetched isobtained.

    ______________________________________    The number of logical blocks to be prefetched (blocks) =    reading speed (Bytes/sec) * prefetching time (sec)/    logical block size (Bytes/block) =    500 * 1024 * 4.77/512 =    4770 (blocks)    ______________________________________

On the basis of this result, a prefetching start logical block addressis obtained.

    ______________________________________    prefetching start logical block address =    the final recording position of data recorded in the    optical disk "disk#1" - the number of logical blocks to be    prefetched + 1 =    8191 - 4770 + 1 =    3422    ______________________________________

In step 5, the control means 102 controls the conveyer 504 in thelibrary unit 500 by the library control means 101 so that the opticaldisk "disk#1" stored in the slot #10 is taken out of the storage shelf502 and mounted in the optical disk drive 503. The control means 102transmits data read from the optical disk "disk#1" mounted in theoptical disk drive 503, through the data transmitting and receivingmeans 103 in the server unit 100 and the network 650, to the datatransmitting and receiving means 704 in the client 700. In the client700, the compressed data are expanded by the MPEG decoder of the datareproducing means 707 and displayed on the display unit 703.

In step 6, the control means 102 judges whether or not the readingposition of the multimedia data "multi01" reaches the prefetching startlogical block. When the reading position does not reach the logicalblock, step 10 is executed to continue reading and reproduction and,after judging whether the reproduction is ended in step 11, the controlmeans 102 returns to step 6. Thereafter, until the control means 102judges that the prefetching start recording position is reached, steps 6to 10 and step 11 are repeated, and reading and reproduction ofmultimedia data from the optical disk are continued.

When the control means 102 judges in step 6 that the prefetching startposition is reached, the control means 102 proceeds to step 7 whereinprefetching of data is started from the prefetching start logical block.The prefetched data are stored in the temporary storage means 111.

When the prefetching in step 7 is ended, the control means 102 startsexchange of optical disks. The optical disk "disk#3" is mounted in thedrive in the same manner as described for step 5. On the other hand, instep 8, the control means 102 judges whether the optical disk is in theprocess of being exchanged. When the optical disk is in the process ofbeing exchanged, the control means 102 proceeds to step 9 wherein thedata transmitting and receiving means 103 transmits the data stored inthe temporary storage means 111, through the network 650, to the client700. In the client 700, the transmitted data are reproduced.

The control means 102 confirms that all the data stored in the temporarystorage means 111 are transmitted. Then, in step 10, the control means102 instructs the library control means 101 and the data transmittingand receiving means 103 to start reading and transmission of multimediadata "multi01" from the optical disk "disk#3". Thereafter, therespective steps mentioned above are repeated until the control means102 judges in step 11 that the reproduced is ended.

As described above, in the multimedia server system according to thesixth embodiment of the invention, when multimedia data recorded overplural optical disks is reproduced, the control means calculates thedata position from which prefetching is started so that a portion of themultimedia data equivalent to the optical disk exchange time is storedin the temporary storage means, and prefetching and temporary storageare performed while performing reading and reproduction of multimediadata. Therefore, the data stored in the temporary storage means istransmitted during exchange of the optical disks, the reproduction ofthe multimedia data is not interrupted, that is, continuous reproductionis realized.

Embodiment 7

A multimedia server system according to a seventh embodiment of thepresent invention is identical to the system according to the sixthembodiment in that data equivalent to the time required for exchange ofdisks is temporarily stored, and the server system according to thisseventh embodiment can deal with a request for jumping reproduction.

The structure of the multimedia server system and the recording state ofmultimedia data according to this seventh embodiment are identical tothose mentioned for the sixth embodiment. The operation of the serversystem when multimedia data are reproduced in response to a request fromthe client is identical to that according to the sixth embodiment.However, only when the client outputs a request for jumping reproductionand a logical block address to which the jumping reproduction is givenis positioned after a prefetching start logical block address calculatedin advance, the operation of the server system differs from thatmentioned for the sixth embodiment.

FIGS. 19(a) and 19(b) are diagrams for explaining problems in thejumping reproduction. As shown in FIG. 19(a), in ordinary reproductionin the server system according to the sixth or seventh embodiment of theinvention, when multimedia data recorded over plural disks isreproduced, a portion of the multimedia data equivalent to the diskexchange time is prefetched and stored in the temporary storage means.As described for the sixth embodiment, since this data is read andreproduced during the disk exchange time, continuous reproduction isrealized. FIG. 19(b) shows a case where a request for jumpingreproduction is positioned after the prefetching start position. In thiscase, if the prefetching and temporary storage are performed from thedesignated reproduction start position, the amount of the multimediadata stored in the temporary storage means is insufficient when the disk"disk#1" is exchanged for the next disk "disk#3", resulting in aninterruption in the reproduction due to the exchange of the disks.

This problem is solved in the multimedia server system according to thisseventh embodiment of the invention. That is, in this system, multimediadata equivalent to the shortage of data in the temporary storage meansis prefetched and stored temporarily and, thereafter, reading, temporarystorage, and reproduction are performed from the designated position,whereby unwanted interruption in the reproduction due to exchange of thedisks is avoided.

Hereinafter, the operation of the multimedia server system according tothis seventh embodiment will be described for a case where a request forjumping reproduction from the client 700 designates, as a recordingposition on the optical disk, a position after the prefetching startposition which is calculated in advance. It is assumed that theprefetching start position corresponds to a logical block address 3422,and a logical block address 4000 is designated as the reproduction startposition.

When the control means 102 receives a request for Jumping reproductiondesignating a starting logical block address 4000 from the client 700through the data transmitting and receiving means 103, the control means102 compares the reproduction starting logical block address with theprefetching starting logical block address calculated according to thesixth embodiment, and finds that the reproduction starting logical blockaddress 4000 is positioned after the prefetching starting logical blockaddress 3422.

Then, the control means 102 prefetches multimedia data between theprefetching starting logical block address 3422 and the reproductionstarting logical block address 4000, and stores the prefetched data inthe temporary storage means 111.

When the prefetching is ended, the control means 102 starts reproductionof the multimedia data requested by the client 700, from the logicalblock address 4000. That is, although the multimedia data between thelogical block addresses 3422 and 4000 is read in the temporary storagemeans and read out from the temporary storage means, this data is notreproduced in this stage. When reading of data after the requestedaddress 4000 is started, the data between the logical block addresses3422 and 4000 is transmitted and reproduced. The operation of the serversystem according to the seventh embodiment other than theabove-mentioned operation is identical to the operation of the serversystem according to the sixth embodiment.

As described above, in the multimedia server system according to theseventh embodiment of the invention, when a jumping reproduction isrequested after the prefetching starting logical block address,multimedia data between the prefetching starting logical block addressand the reproduction requested logical block address is stored in thetemporary storage means. Therefore, shortage of the prefetchedmultimedia data due to the request of jumping reproduction is avoided,whereby unwanted interruption in the reproduction of multimedia data isavoided even when the jumping reproduction is requested.

Embodiment 8

In a multimedia server system according to an eighth embodiment of theinvention, when a request for reproduction of multimedia data from aclient is given to an optical disk which is in the process ofreproduction, the request is refused to avoid interruption inreproduction.

In this eighth embodiment, the structure of the multimedia serversystem, the hardware structures of the server and the client, thestructure of the client, and the structure of the library unit are thesame as those according to the first embodiment of the invention.

FIG. 20 is a block diagram illustrating a server unit 100 according tothe eighth embodiment of the invention. In FIG. 20, reference numeral115 designates a recording media storage means for storingcorrespondences between plural multimedia data and identificationnumbers of optical disks in which the multimedia data are recorded.Reference numeral 116 designates an identification number comparingmeans for comparing the identification numbers of the optical disks. Thesame reference numerals as those shown in FIG. 16 designate the same orcorresponding parts. FIG. 21(a) shows a data structure in the recordingmedia storage means 115, and FIG. 21(b) shows specific data stored inthe storage means 115.

In the server system so constituted, as in the sixth embodiment of theinvention, two multimedia data "multi01" and "multi02" are recorded inoptical disks contained in the library unit 500, more specifically, theformer is recorded over two optical disks "disk#1" and "disk#3", and thelatter is recorded over three optical disks "disk#2", "disk#3", and"disk#4". The recording media storage means 115 contains data shown inFIG. 21(b).

The operation of the server system according to this eighth embodimentwill be described on the assumption that two clients 700 and 701 areconnected to the network, reproduction of the multimedia data "multi01"has already started in the client 700, and the client 701 outputs arequest for reproduction of the multimedia data "multi02".

The control means 102 checks the contents of the recording media storagemeans 115 and finds that the requested data "multi02" is recorded overthree optical disks, identification numbers of which are "disk#2","disk#3", and "disk#4", respectively, and that the data "multi01", forwhich reproduction has already started, is recorded over two opticaldisks, identification numbers of which are "disk#1" and "disk#3",respectively. Then, the control means 102 compares the identificationnumbers of the optical disks stored in the recording media storage means115 with each other by the identification number comparing means 116.The identification number comparing means 116 informs, to the controlmeans 102, that one of the optical disks having the multimedia data"multi02" has the same identification number as "disk#3" of the opticaldisk having the multimedia data "multi01" which is now in the process ofbeing reproduced. Then, the control means 102 refuses the request forreproduction of "multi02" from the client 701.

In the server system according to the eighth embodiment, when therequest from the client is not refused in the above-mentioned stage, thesame operation as described for the sixth embodiment is performed toreproduce the requested multimedia data.

As described above, according to the eighth embodiment of the invention,the server system is equipped with the recording media storage meansthat stores identification numbers of optical disks in which pluralmultimedia data are recorded, for each multimedia data, and theidentification number comparing means. The identification numbercomparing means compares identification numbers of optical disks havingmultimedia data which is in the process of reproduction withidentification numbers of optical disks having newly requestedmultimedia data. When the new request is given to the optical disk inthe process of reproduction, the request is refused because reading ofplural multimedia data from the same disk exceeds the performance of theoptical disk drive. As already described for the prior art system, in anoptical disk drive that is inferior in performance than a magnetic diskdrive, when plural multimedia data are reproduced from the same disk,reading of the data delays, adversely affecting the reproduction of themultimedia data. However, since the server system according to thiseighth embodiment inhibits such a reproduction, undesired interruptionin reproduction is avoided.

Embodiment 9

A multimedia server system according to a ninth embodiment of theinvention checks requests for reproduction of multimedia data fromclients and refuses to accept the request exceeding the reproducibilityof the system, whereby unwanted interruption in the reproduction isavoided.

In this ninth embodiment, the structure of the multimedia server system,the hardware structures of the server and the client, the structure ofthe client, and the structure of the library unit are identical to thoseaccording to the first embodiment of the invention.

FIG. 22 is a block diagram illustrating a server unit 100 according tothe ninth embodiment of the invention. In FIG. 22, reference numeral 117designates a reproducible number storage means storing the number ofmultimedia data that can be reproduced simultaneously from each opticaldisk in the optical disk library unit 500. Reference numeral 118designates a reproduction number storage means storing a reproductionnumber which is the sum of the number of multimedia data which is/are inthe process of being reproduced and the number of multimedia data whichis/are to be reproduced. In FIG. 22, the same reference numerals asthose shown in FIG. 16 designate the same or corresponding parts. FIG.23(a) shows a data structure in the reproduction number storage means118, and FIG. 23(b) shows specific data of the content stored in thestorage means 118.

It is assumed that the number of multimedia data that can be read from asingle optical disk is 2, so that "2" is stored in the reproduciblenumber storage means 117. Three clients 700, 701, and 702 are connectedto the server system through the network, and multimedia data "multi03"and "multi04" are already reproduced by the clients 700 and 701,respectively. The multimedia data "multi03" is recorded over two opticaldisks, identification numbers of which are "disk#1" and "disk#2",respectively, and the multimedia data "multi04" is recorded over twooptical disks, identification numbers of which are "disk#2" and"disk#3", respectively. The reproduction number storage means 118 storesdata shown in FIG. 23(b).

The operation of the server system according to this ninth embodimentwill be described for a case where the client 702 requests forreproduction of multimedia data "multi06" which is recorded over twooptical disks, identification numbers of which are "disk#1" and"disk#2".

When the request for reproduction of "multi06" from the client 702 istransmitted through the network to the server unit 100, the controlmeans 102 receives the request through the data transmitting andreceiving means 103.

The control means 102 checks the contents of the reproducible numberstorage means 117 and finds that the number of multimedia data that canbe reproduced simultaneously from each optical disk is 2. Then, from thecontents of the reproduction number storage means 118, the control means102 finds that the reproduction number of the optical disk "disk#1" is 1and the reproduction number of the optical disk "disk#2" is 2, whichdisks have the data "multi06".

Next, the control means 102 adds 1 to the reproduction number of eachoptical disk having the data "multi06". As a result, the reproductionnumber of the optical disk "disk#1" becomes 2, and the reproductionnumber of the optical disk "disk#2" becomes 3. Then, the control means102 compares the result for each optical disk with the simultaneouslyreproducible number of multimedia data, i.e., 2, stored in thereproducible number storage means 117. Since the reproduction number ofthe optical disk "disk#2", i.e., 3, is larger than 2, the control means102 refuses the request for reproduction of "multi06" from the client702.

In the server system according to this ninth embodiment, when therequest from the client is not refused in the above-mentioned stage, thesame operation as described for the sixth embodiment is performed toreproduce the requested multimedia data.

As described above, the multimedia server system according to this ninthembodiment is equipped with the reproducible number storage means thatstores the number of multimedia data which can be reproducedsimultaneously from each optical disk, and the reproduction numberstorage means that stores the reproduction number which is the sum ofthe number of multimedia data being reproduced now and the number ofmultimedia data to be reproduced later. When the server system receivesa request for reproduction of multimedia data, 1 is added to thereproduction number of each optical disk having the requested multimediadata and judges whether the result of the addition exceeds the number ofthe reproducible multimedia data. When it exceeds that number of theoptical disk, the request is refused. Therefore, unwanted interruptionin reproduction due to reproduction exceeding the ability of the opticaldisk drive is avoided.

Embodiment 10

A tenth embodiment of the present invention relates to an apparatus forcontinuously reproducing multimedia data recorded over plural disks.

FIG. 24 is a block diagram illustrating a hardware structure of thereproduction apparatus according to the tenth embodiment of theinvention. In FIG. 24, a disk I/F 301, a real-time clock 303, a CPU 304,a main storage unit 305, a magnetic disk unit 307, and an optical disklibrary unit 500 are identical to those shown in FIG. 2(a) (206, 202,204, 205, 207, and 500, respectively). Further, an MPEG decoder 302, adisplay speaker 308, a display I/F 309, and a keyboard or mouse 310 areidentical to those shown in FIG. 2(b) (211, 208, 209, and 210,respectively).

FIG. 25 is a block diagram of the reproduction apparatus viewed from thefunction. In FIG. 25, a library control means 101, a control means 102,an operating state storage means 104, a reproduction order storage means105, a reproduction time storage means 106, and an exchange time storagemeans 109 are identical to those shown in FIG. 3 according to the firstembodiment. Further, a reproduction request accepting means 121, areproduction time measuring means 122, a data reproducing means 123, anda display 124 are identical to those shown in FIG. 4 (706, 705, 707, and703, respectively) according to the first embodiment. Thecorrespondences between the hardware constituents shown in FIG. 24 andthe functional constituents shown in FIG. 25 are the same as thosementioned for the first embodiment.

The operation of the reproduction apparatus according to this tenthembodiment is identical to the operation of the server system accordingto the first embodiment except the operation of reproducing multimediadata in step 10 of the flowchart shown in FIG. 6.

In step 10, the control means 102 transmits multimedia data read fromthe optical disk "disk#0" mounted in the optical disk drive "Drive0" tothe data reproducing means 123, wherein the MPEG compressed data isexpanded by the MPEG decoder and displayed on the display 124.

In the operation, the request for reproduction accepted by thereproduction request accepting means 121 and the result from thereproduction time measuring means 122 are transmitted directly to thecontrol means 102, not through the data transmitting and receiving meansand the network.

As described above, also in the multimedia reproduction apparatusaccording to this tenth embodiment, as in the server-client systemaccording to the first embodiment, multimedia data recorded over pluraloptical disks can be reproduced without interruption due to exchange ofthe disks.

The apparatus may be provided with, in place of the operating statestorage means, a reservation data storage means and a clock as in thesecond embodiment of the invention.

When the structure according to this tenth embodiment is applied to theserver unit in the multimedia server system according to the first orsecond embodiment, reproduction of multimedia data is realized in theserver unit. In this case, the result of reproduction in the client canbe confirmed by the server.

Embodiment 11

An eleventh embodiment of the present invention relates to an apparatusfor continuously reproducing multimedia data recorded over plural disks.

The hardware structure of the reproduction apparatus according to thiseleventh embodiment is identical to that shown in FIG. 24 according tothe tenth embodiment.

FIG. 26 is a block diagram of the reproduction apparatus viewed from thefunctions. In FIG. 26, a library control means 101, a control means 102,and a disk exchange time storage means 109 are identical to those shownin FIG. 3 according to the first embodiment. A temporary storage means111, a data recording position storage means 112, a reading speedstorage means 113, and a reproducing speed storage means 114 areidentical to those shown in FIG. 16 according to the sixth embodiment. Areproduction request accepting means 121, a data reproducing means 123,and a display 124 are identical to those shown in FIG. 4 (706, 707, and703, respectively) according to the first embodiment. Thecorrespondences between the hardware constituents shown in FIG. 24 andthe functional constituents shown in FIG. 26 are the same as thosementioned for the first embodiment.

The operation of the reproduction apparatus according to this eleventhembodiment is identical to the operation of the server system accordingto the sixth embodiment except steps 5, 9, and 10 for reproducingmultimedia data, in the flowchart shown in FIG. 18. More specifically,in this eleventh embodiment, the control means 102 transmits data readfrom the optical disk or the temporary storage means 111 to the datareproducing means 123, wherein the MPEG compressed data is expanded bythe MPEG decoder and displayed on the display 123.

In the operation, the request for reproduction accepted by thereproduction request accepting means 121 and the result from thereproduction time measuring means 122 are transmitted directly to thecontrol means 102, not through the data transmitting and receiving meansand the network.

As described above, also in the multimedia reproduction apparatusaccording to this eleventh embodiment, as in the server-client systemaccording to the sixth embodiment, multimedia data recorded over pluraloptical disks can be reproduced without interruption due to exchange ofthe disks.

While the structure of the apparatus according to this eleventhembodiment is based on the server system according to the sixthembodiment, it may be based on the server system according to the thirdor fourth embodiment to realize a continuous reproduction by reading andreproducing data temporarily stored during exchange of disks.

In the multimedia server system according to any of embodiments 3 to 6,when the structure according to this eleventh embodiment is applied tothe server unit, reproduction of multimedia data in the server unit ispossible. In this case, the result of reproduction in the client can beconfirmed by the server.

What is claimed is:
 1. A method for reproducing multimedia data recordedover plural optical disks, using an optical disk library unit having atleast two, first and second, optical disk drives, the method comprisingsteps of:reading and reproducing multimedia data recorded in one of theoptical disks in the first optical disk drive and, during the readingand reproduction, mounting the next optical disk in the second opticaldisk drive; and starting reading and reproduction of multimedia datarecorded in the next optical disk mounted in the second optical diskdrive immediately after the reading of the multimedia data recorded inthe optical disk in the first optical disk drive is completed.
 2. Themethod of claim 1 comprising steps of:storing order of the pluraloptical disks to reproduce the multimedia data from the optical disks,and a time required for the reproduction of the multimedia data fromeach optical disk; storing operating state of each optical disk drive inthe optical disk library unit; reading and reproducing the multimediadata recorded in the optical disk in the first optical disk drive;mounting the next optical disk, according to the stored reproductionorder, in the second optical disk drive that is judged as usable on thebasis of the stored operating state of the second optical disk drive,during the recording and reproduction, when the remaining reproductiontime of the optical disk in the first optical disk drive, which time isobtained by subtracting the time taken by the reproduction from thestored time required for the reproduction, is longer than the timerequired for exchange of optical disks; and starting reading andreproduction of the multimedia data recorded in the next optical diskmounted in the second optical disk drive immediately after the readingof the multimedia data recorded in the optical disk in the first opticaldisk drive is completed.
 3. The method of claim 1 comprising stepsof:storing order of the plural optical disks to reproduce the multimediadata from the optical disks; deciding, for each optical disk, an opticaldisk drive used for reading and reproduction of the multimedia data fromthe optical disk, and a period of time the optical disk drive is used,and storing these as reservation data; and mounting the optical disk inthe optical disk drive according to the stored reproduction order andthe reservation data when the present time reaches the decided time, andreading and reproducing the multimedia data from the optical disk.
 4. Amultimedia server system comprising an optical disk library unit whereinmultimedia data recorded in plural optical disks are processed with atleast two, first and second, optical disk drives, and a server fordistributing the multimedia data recorded in the optical disks to pluralclients, said system being characterized by:a reproduction order storagemeans for storing the order of the plural optical disks to reproduce themultimedia data from the optical disks, and storing storage places ofthe optical disks in the optical disk library unit; an operating statestorage means for storing the operating state of each optical diskdrive; and a control means for controlling reading of multimedia datafrom the optical disk library unit and distribution of the multimediadata to the clients, in response to requests for reproduction ofmultimedia data from the clients; wherein, when multimedia data recordedover some of the optical disks is requested, during reading andreproduction of the requested multimedia data from one of the opticaldisks in the first optical disk drive, the control means takes the nextoptical disk having the requested data from the storage place accordingto the content of the reproduction order storage means, mounts theoptical disk in the second optical disk drive that is judged as usableaccording to content of the operating state storage means, and startsreading and reproduction of the multimedia data from the next opticaldisk immediately after the reading from the optical disk in the firstoptical disk drive is completed.
 5. A multimedia server systemcomprising an optical disk library unit wherein multimedia data recordedin plural optical disks are processed with at least two, first andsecond, optical disk drives, and a server for distributing themultimedia data recorded in the optical disks to plural clients, saidsystem being characterized by:a reproduction order storage means forstoring the order of the plural optical disks to reproduce themultimedia data from the optical disks, and storing storage places ofthe optical disks in the optical disk library unit; a reproduction timestorage means for storing the time required for reproduction ofmultimedia data from each optical disk; an exchange time storage meansfor storing the time required for exchange of the optical disks; areservation data storage means for storing, for each optical disk havingmultimedia data requested by the client, an optical disk drive to beused for reproduction of the requested data, and the reservation timeobtained by adding the time required for exchange the optical disks tothe time required for the reproduction; and a control means forcontrolling reading of multimedia data from the optical disk libraryunit and distribution of the multimedia data to the clients, in responseto requests for reproduction of multimedia data from the clients;wherein, when a request for reproduction of multimedia data is given tothe control means, the control means updates the contents of thereservation data storage means according to the request, referring tothe contents of the reproduction order storage means, the reproductiontime storage means, the exchange time storage means, and the reservationdata storage means, and then the control means controls mounting of theoptical disk having the requested data, and reading and reproduction ofthe requested data.
 6. The multimedia server system according to claim 4further comprising:a recording media storage means for storing, for eachmultimedia data, an identification data that shows an optical disk inwhich the multimedia data is recorded; an identification data comparingmeans for comparing the identification data of the plural optical diskswith each other; and said control means accepting or refusing therequest for reproduction of multimedia data from the client, on thebasis of the result of the comparison by the identification datacomparing means.
 7. The multimedia server system according to claim 4further comprising:a reproducible data number storage means for storingan upper limit of the number of multimedia data that can be reproducedsimultaneously from each optical disk; a reproduction number storagemeans for storing a reproduction number of each optical disk, whichreproduction number is the sum of the number of multimedia data beingreproduced from the optical disk and the number of multimedia data to bereproduced later from the optical disk; and said control means acceptingor refusing the request for reproduction of multimedia data from theclient, on the basis of the contents of the reproducible data numberstorage means and the reproduction number storage means.